[ntp:questions] ntpd: time reset problem
David J Taylor
david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Fri Sep 18 05:52:54 UTC 2009
"David Lord" <snews at lordynet.org> wrote in message
news:7hg1jtF2s1lvqU1 at mid.individual.net...
> David J Taylor wrote:
>> You'll have to get a GPS puck and wireless PC on the roof! Safely
> That looked a possibility earlier this year but treeline front
> and back has shot up maybe a couple of metres already and if
> same next year I'd be needing a mast.
Don't worry about trees - a modern GPS such as the GPS 18x LVC is very
sensitive, and can work with a lot of obscuration. Although my GPS 18 LVC
is sitting on the roof, the GPS 18x LVC works just as well sitting in a
room on the top floor of the house.
> I'm signed up in protest at various network over mains systems
> due to them splattering and killing QRP reception.
> I've not mastered the demodulation though and whilst on scope
> it looks to be a clean and identifiable MSF timecode no
> different than from Conrad module, a much closer look shows
> noise spikes. I used an RC filter at output and suspect a
> Schmitt as with Maplin circuit is needed.
What sort of filtering is used these days? I used to think a 60KHz
crystal was required, with a bandwidth of a few 10's or 100's of Hz (there
used to be a fast-code transmission on the signal). What's the rise-time
required through the filter? 20ms fast enough? A Schmitt trigger would
be worth trying, because although there will be some hysteresis on the PC
input port, it will be more appropriate for RS-232 levels and not tailored
to your signal.
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